Centrifugal casting machine



0a. 6, m2. E: O RE' 2,297,973

CENTRIFUGAL CASTING MACHINE .Filed Aug. 11, 1941 2 Sheets-Sheet 2INVTOR.

Patented Oct. 6, 1942 iJNiTED STATES i t i'ihfi'i QFFICE CENTRIFUGALCASTING MACHINE Emmett B. Moore, Evanston, Ill.

7 Application August 11, 1941, Serial No. 406,252

10 Claims.

This invention relates to casting machines of the centrifugal typeemployed in the casting of small articles of gold or other similarmetals, as for example in making inlays or large fillings for dentalwork, or articles of jewelry.

One object of the invention is to provide a smoothly running mechanismwith an articulated connection between the crucible and mold carryingparts and a rotatable driving member, together with means to controlsaid crucible and mold in their response to centrifugal and inertiaforces and to cause these parts to assume positions such as to avoidsplashing or spilling of the molten metal during the initial portion ofthe rotary movement.

Another object is to provide means for holding the articulated partsagainst pivotal movement during preparation of the crucible and mold andmounting of these latter in the machine.

It is also an object of the invention to provide a plurality of controlmeans to govern the initial movement of the articulated connection, suchmeans to be employed selectively in accordance with the weight and othercharacteristics of the particular mold to be 'used in the machine.

Other objects and advantages will appear as the description proceeds.The invention consists in certain features and elements of constructionin combination, as herein shown and-described and as indicated by theclaims.

In the drawings:

Figure 1 is a side elevation of a centrifugal casting machine embodyingthis invention show- .ing the articulated connection at fully extendedposition.

Figure 2 is a topplan view of themachine with the parts in the sameposition as in Figure -1.

Figure 3 is a detail section taken substantially -as indicated at line3-3 on Figure 1.

the action of centrifugal force.

Figure 7 is'a partial side elevation of the machine showing it fittedwith amold ring of different size from that'shown'in Figure 1.

In the casting of gold or like metals in producing relatively smallarticles, such as dental fillings and inlays and small pieces ofjewelry, the molten metalin the crucible-must beztransferred to the moldquickly and under some pressure to ensure accurately filling the moldand especially its narrower passages and more delicate features, and toensure that no air shall be pocketed therein. In a centrifugal machineof this type .the crucible containing the molten metal and the mold towhich it is to .be transferred are mounted in communicating relation andfor rotation about an axis so positioned that the centrifugal forcegenerated by the rotation shall act to transfer the metal from thecrucible into the mold. The machine herein illustrated is in generalsimilar to that shown .and described in my co-pending application.Serial No. 327,160 filed April 1, 1940, which includes a motor spring.to be wound up to the desired tension and then released suddenly forstarting the rotation of the parts ,by which the mold and crucible arecarried. A one-way clutch permits the parts to continue rotating afterthe spring has expended its force so that the centrifugal force maycontinue to act while the metal is cooling and hardening in the mold.

But in machines of this type it has been a difiicult problem to initiatethe rotation of the gold suddenly and forcibly without causing the metalto splash or spill from the crucible before it has time to flow into themold. The sudden application of :the force of the spring in starting thecrucible from rest tends to accelerate the crucible at a rapid ratewhile the inertia of the molden gold causes the gold itself to lag,

so that the crucible is actually moved out from .under-thegold tosomeextent. This would cause a portion .of the fluid metal to spill overthe ,edgesof .the crucible unless the latter were positioned in exactlycorrect relation to the forces acting on the gold. In order to takeadvantage of this inertia of the molten metal instead of allowing itthus to cause lossand possibledamage the present machine is designed toautomatically change the position of the mold and .crucible withreference to their path of rotation during the initial portion of thismove- ;ment in such a way as to .keep them adjusted .in substantialalignment with the resultant of inertia and centrifugal forces, so thatthe inertia tends to shift the gold toward and into the mold rather thanover the sides of the crucible and is then supplemented by thecentrifugal force as soon as sufficient speed is acquired in themovement.

As shown in the drawings, the machine in- :cludes a hollow base I whichmaybe understood as enclosing a motor springarranged to rotate avertical shaft 2 journaled within the base and having a head 3 at itsupper end in which there is secured a horizontally extending arm orcrossbar 4. The longer end of the cross-bar 4 carries an adjustableweight 5 which may be shifted to approximately balance the rotatableelements of the machine, and the shorter end of the bar is provided witha projecting flat lug or plate 6 serving as one element of a. hinge tosupport a swinging or "floating arm I which carries the crucible andmold. A bolt 8 acting as the hinge pivot extends through the lug 6 andthrough cylindrical portions 9, 9 of a bifurcated bracket arm ID towhich the arm I is attached. The arm I carries at its outer end arigidly attached upstanding plate II which supports a holder I2 for themold ring shown at I3, and the crucible I 4-is carried by a bracket I5which includes a sleeve I5 adjustable along the arm I. A clutch orgripping device of any suitable construction such as that described inmy co-pending application No. 327,160 may be enclosed within the arm Iand sleeve I6 and provided with an operating member in the form of aknurled ring I! threaded on to the end of the sleeve I6 for clamping thesleeve and the bracket I5 at any desired position of adjustment alongthe arm I.

Just below the plane of rotation of the crossbar 4 the base I carries acam plate which, as shown in the drawings, includes two spiral cams 2Iand 22 respectively. The initial and terminal radii of the two cams aresubstantially the same but the cam 2I extends through a considerablygreater angle than the cam 22. The terminal portion of each cam surfaceis spaced radially from the initial portion of the other cam surface soas to form notches or recesses 2Ia and 22a which are dimensioned toreceive a cylindrical lug or follower 23 rigidly attached to thebracketI0 and depending therefrom as seen in Figure 1. When the spring withinthe base I has been tensioned by reverse rotation of the cross-bar 4 tothe desired extent the floating arm I is swung about the pivot 8 to theposition shown in Figure 3 so that the lug 23 can enter the notch 2 Ia(or 22a).

At this position one of the notches 24 in a locking disc 25 which isfixed to the shaft or spindle 2, as seen in Figure 3, is engaged with alocking dog 26 extending inside the upper portion of the base I so as toprevent rotation of the parts while the gold is being placed in thecrucible I4 and melted therein and while the mold ring, which is heatedin an electric furnace just prior to the casting operation, is beingtransferred to the casting machine and secured in its holder I2. Thetension of the spring maintains engagement between the edge of the notch24 and the locking dog 26 but the length of the notch 2Ia (or 22a) isenough to allow the crossbar 4 to be swung slightly against the tensionof the spring so as to relieve this pressure, whereupon, the locking dog26, being carried in a vertical slot 21 in the base housing, will dropby gravity out of engagement with the notched disc 25 so that uponmanual release of the bar 4 the spring will start rotating the shaft 2with the cross-bar and its hinged floating arm I. A button 28 isattached to the'locking dog 26 and is exposed outside the base housingI, for again lifting the locking dog 26 into active'position whenrequired.

The gold is usually melted in the crucible I4 by means of a small blowtorch and in order to determine when it is in proper molten conditionfor casting, it is desirable to jiggle or vibrate the crucible slightlyin a horizontal plane. As indicated in Figure 3, the length of the notch2Ia (or 2211) is suflicient to allow this to be done without releasingthe follower 23, and the notch 24 is considerably wider than the dog 26,so that said dog 26 may be held up in its locking position withoutinterfering with this shaking or jiggling procedure.

As shown in Figure 4 the hinged floating arm I at starting positionextends at slightly less than degrees to the direction of the cross-bar4. The crucible and the mold are in substantial alignment along the arm'I with the crucible standing ahead of the mold with reference to thedirection in which the parts are to rotate as indicated by the arrow R.Thus when the rotation starts the crucible and mold will trail fromtheir pivotal connection with the cross bar at 8, and upon the suddenapplication of the force of the spring to initiate the rotation, thecrucible and mold will move forward (in the direction of the arrow B)more quickly than the molten gold in the crucible, the inertia of thegold itself tending to hold it fixed in its original position in space.The quick forward motion of the crucible will thus act to slip it fromunder the gold forcing the gold or a portion of it to pass through theconnecting passageway into the mold in the ring I3.

Meanwhile the rapid acceleration of the rotary movement of the cross-bar4 generates centrifugal force tending to swing the floating arm 1 aboutthe pivot 8 and carry the mold and crucible outwardly, that is, topositions farther from the axis of rotation. But experience has proventhat the inertia of these parts delays their prompt response to thecentrifugal force, whereas the molten gold in the crucible I4 will beaffected by the centrifugal force more promptly than the connected groupof parts carried by the floating arm I. As a result, if the arm 'I weremerely allowed to adjust itself in response to centrifugal and inertiaforces it would not move quickly enough to prevent some of the moltengold from spilling over the side of the crucible in the initial portionof the rotation--say, within the first twenty or thirty degrees thereof.Therefore I have provided the cam plate 20 with its spiral contour 2Iextending from the notch 2Ia and its spiral contour 22 extending fromthe notch 22a so that as the follower lug 23 leaves one or the other ofthese notches at the commencement of rotation, the corresponding spiraledge of the cam plate will engage the lug 23 and force the arm 'I toswing outwardly at a rate controlled by the shape of the spiral. Thisrate is such as to maintain the crucible andmold in substantialalignment with the changing direction of combined inertia andcentrifugal forces as the rotating parts pick up speed. In other words,the mold in the ring I3 is kept in line with the natural path which thegold tends to follow and is thus in position to receive the gold in theinitial portion of the rotation of the device. Figure 5 indicates thechange in angular relation between floating arm I and the cross-bar 4which is effected by the travel of the follower 23 along the cam 2| inapproximately of a revolution. As the follower 23 passes the end of thecam surface the centrifugal force will have become sufficient to swingthe arm I farther outward into alignment with the cross-bar 4 as shownin Figure 6, and in this position it will continue to rotate under themomentum acquired from the force'of the spring, l.thus allowing time forthe casting-to harden in the mold. A friction brake button at 29 may beemployed if it-is desired to :check the rotation before themomentum-isexwork the ring l3 will accommodate most bridges and specialdentures While a smaller ring i aas shown in Figure 7 will take care ofthe smaller castings such as inlays. While the holder or cradle l2 forthe ring l3 is-securedclosely against the plate H at the end of the armI, I ,prefer to provide the cradle 32 for the'ring 33 with a stem '31 bywhich it is spaced away from'the plate-ll by a distance equal to'thediiferencebetween the lengthof ring [3 and the length of ring-'33. Thenwith either ring in place, the crucible M will stand at the sameposition on the arm 'l and the samecam 2! will provide the correctcontrol of the floating arm 1 to insure delivery'of all the gold to themold without splashing or spilling over the side of the crucible.

When the machine is used in the manufacture or repair of jewelry a stilllonger ringmay be required as indicated in dotted outline atdt in Figure'7, in which case the crucible M inust be moved back to a positionnearer the center-of rotation. At this shorter radius the centrifugalforce Will be less effective on the molten gold-in the crucible at thebeginning of rotative movement; but, on the other hand thegreater weightof the large mold and its ring 53 gives them more inertia and rendersthe floating assembly more sluggish in responding to centrifugal forceas the device gains speed. Hence, to insure a sufficiently promptoutward swing of the arm 'i about its hinge pivot 8, when carrying thislarger mold ring 43, the follower lug 23 is backed into the notch 22a,and the steeper cam 22 operates to control the movement for preventingsplashing or spilling of the gold.

The extent to which the spring motor is ten sioned for any particularcasting is within control of the operator, but in general, for castings,such as inlays, made in the small ring 33, the arm 4 will be turnedbackward to wind up the spring to the extent of two full turns; with thelarger ring l3, it will begiven four turns; and for the largest ring 43,the spring will be wound up to six turns. Intermediate tensions may bechosen, if desired, since the looking disc 25 has four notches and thearm 4 can thus be locked at each quarter turn. The adjustment of initialtension is intended to compensate for the differences in weight of thedifferent molds and the gold employed with them and to get the machineunder way at about the same speed in each case.

While there is shown and described herein certain specific structure, itwill be manifest that various changes and re-arrangements may be madewithout departing from the spirit and scope of the invention, and thatit is not limited to the form herein disclosed, except in so far asindicated by the appended claims.

I claim as my invention:

1. In a centrifugal casting machine, a base, a cross-bar mounted forrotation thereon, a mold and crucible support with pivotal meansconnecting said support to the bar at a distance from the axis ofrotation, the support being free to be swung inwardly about said pivotalconnection before the rotation of the bar begins and to be swung outwardby the centrifugal force generated by-the rotation, 'a substantiallyspiral cam onthe base anda fellower on the support positio'nedto engagethe cam in the initial portion of said rotation, said cam acting toovercome the' in'ertia of the mold support and to positively swing thesupport outwardas the bar beginstotur'n.

2. In a centrifugal casting machine, a base a cross-bar'mounted forrotation thereon, a mold and crucible support with pivotal meansconnecting said support to the bar at a distance from the axis ofrotation, the support being free 'to-be swung inwardly abcut saidpivotal connection before'the rotation of the bar begins and tobe swungoutward by the centrifugalforce generated by the rotation, andmechanical means acting positively to swing the-support outwardly-in theinitial portion of the rotation of the bar.

3. In a centrifugal casting machine, a base, a cross-bar mounted forrotation thereon, a mold and crucible support with pivotal--means-conmeeting said support to the bar at a distance'from the axisof rotation, the support being freeto be swung inwardly about saidpivotal connection'before the rotation of the bar begins and to be swungoutward by the centrifugal force generated by the rotation, the inertiaof the pivoted parts tending to'cause a lag in their response tocentrifugal force as compared with the response of molten metal in thecrucible, and means operative to forcibly overcome such lag andpositively maintain the crucible and. mold in substantial alignment withthe resultant of inertia and centrifugal forces acting on said metal inthe crucible during the-initial portion of the rotation,

to insure delivery of the metal from the crucible to the mold.

4. In a centrifugal casting machine, a base, a cross-bar mounted forrotation thereon, a mold and crucible support with pivotal meansconnecting said support to the bar at a distance from the axis ofrotation, the support being free to be swung inwardly about said pivotalconnection before the rotation of the bar begins and to be swung outwardby the centrifugal force generated by the rotation, and control meanscomprising a cam and a follower, one fixed on said base and the othercarried by said support, positioned for mutual engagement during theinitial portion of the rotation and formed to positively swing thesupport outward as the bar begins to turn.

5. In a centrifugal casting machine, a base, a cross-bar mounted forrotation thereon, a mold and crucible support with pivotal meansconnecting said support to the bar at a distance from the axis ofrotation, the support being free to be swung inwardly about said pivotalconnection before the rotation of the bar begins and to be swung outwardby the centrifugal force generated by the rotation, said mold andcrucible support including a carrier for the crucible adjustable alongthe support to accommodate molds of different sizes, such adjustmentaltering the initial distance of the crucible from the axis of rotation,and a plurality of substantially spiral cams on the base selectivelyengagea'ble with a follower on the support in the initial portion of therotation, each cam being formed to positively swing the support outwardas the bar begins to turn, said cams differing in pitch to adapt themfor use with the crucible at its respectively different positions ofadjustment accommodating the different sizes of molds.

6. In a centrifugal casting machine as defined in claim 1, said camhaving a retaining notch at its inner end formed to receive the followerand hold the support against pivotal movement until said follower leavesthe notch in the initial portion of its rotation.

'7. In a centrifugal casting machine as defined in claim 1, said camhaving a retaining notch at its inner end formed to receive the followerand hold the support against pivotal movement until said follower leavesthe notch in the initial portion of its rotation, together with detentmeans acting to hold the cross-bar against rotation under tension of aspring motor connected for rotating it, said detent means 'beingpositioned for efiecti-ve engagement when the follower is disposed inthe notch at the end of the cam.

8. In a centrifugal casting machine as defined in claim 1, said camhaving a notch at its inner end and of substantial extent incircumferential direction, formed to receive the follower and di-'mensioned to permit shaking or vibrating the crucible support through alimited angle about the axis of rotation without releasing the followerfrom said notch.

9. In a centrifugal casting machine as defined in claim 1, said camhaving a retaining notch at its inner end formed to receive the followerand hold the support against pivotal movement until said follower leavesthe notch in the initial portion of its rotation, together with detentmeans acting to hold the cross-bar against rotation under tension of aspring motor connected'for rotating it, said detent means comprising anotched disc connected to turn with the cross-bar and a locking dog onthe base, adjustable to engage a notch of the disc, the notch beingsubstantially wider than the dog, the dog being positioned to engaged inthe notch of the disc when the follower is disposed in the notch at theend of the cam, said last-mentioned notch being dimensioned to permitshaking or vibrating the crossbar and the crucible through a limitedangle about the axis of rotation without releasing the follower fromsaid notch.

10. In a centrifugal casting machine, a base, a cross-bar mounted forrotation thereon, a mold and crucible support with pivotal meansconnecting said support to the bar at a distance from the axis ofrotation, the support being free to be swung inwardly about said pivotalconnection before the rotation of the bar begins and to be swung outwardby the centrifugal force generated by the rotation, a substantiallyspiral cam on the base and a follower on the support positioned toengage the cam in the initial portion of said rotation, said cam actingto overcome the inertia of the. mold support and to positively swing thesupport outward as the bar begins to turn, said mold and cruciblesupport including an arm with a fixed end plate and an upstandingbracket slidably adjustable on the arm, and supporting the crucible withspace between the end plate and bracket to accommodate a mold ring, anda special cradle for a short mold ring, said cradle having a stem bywhich it is spaced from the end plate and secured thereto, whereby theshort ring can be used with the crucible in the same position on the armas it occupies when used with a longer ring.

EMMZE'IT B. MOORE.

